1. Field of the Invention
The present invention relates to keyboards for personal computer apparatuses for example. Personal computer apparatuses, in particular portable personal computer apparatuses such as notebook-type computer apparatuses, are demanded to be reduced in size so as to improve ease in their carriage. Reduction in the size of computer apparatuses requires reduction in size of accompanying keyboards as long as the keyboards can be easily operated by operators. Thus, such keyboards are demanded to be reduced in size while their structures should be kept in a condition where operators can easily operate the keyboards.
2. Related Art
As shown in FIG. 1, a keyboard 10 in an example of keyboards in the related art has four rows of letter keys 11 disposed thereon, each key actuating a relevant switch provided inside the keyboard 10. A number of keys 11 is the same as a number of switches. A shape of a key top of each key 11 is a square having dimensions of a.times.a. In order to achieve a condition of the keyboard where an operator can easily operate (press) the keys, the dimensions of each key cannot be much reduced. In the example, a is 18 mm and each of vertical and horizontal pitches P.sub.1 and P.sub.2 is 19 mm, where the term pitch referred to a distance between centers of adjacent key tops.
As shown in FIG. 2, such a keyboard as the keyboard 10 shown in FIG. 1 is incorporated in a notebook-type computer apparatus 20. The computer apparatus 20 includes a body 21 and a display panel 22 as shown in the figure. The display panel 22 is rotatively supported on the body 21 through a hinge mechanism 23 provided therebetween.
In such a keyboard 10 in the related art, the size of each key top and the pitch between each adjacent key tops are sufficiently large in order to provide ease in operator's operation thereof as described above. Further, the number of keys is required to be the same as the number of switches contained in the keyboard 10. Thus, in the example, total dimensions of an area in the keyboard required to dispose all the 5 rows of keys including the 4 rows of letter keys 11 amount to approximately 100 mm (vertical dimension A shown in FIG. 1).times.approximately 300 mm (horizontal dimension B shown in FIG. 1). The size of the computer apparatus 20 shown in FIG. 2 containing the keyboard 10 is approximately 260 mm (vertical dimension C shown in FIG. 2).times.approximately 300 mm (horizontal dimension D shown in FIG. 2), the same as the A-4 size.
The size a.times.a of the key top of each key 11 and the pitch P.sub.1 and P.sub.2 between each adjacent keys 11 are assumed to be reduced for the purpose of miniaturizing the overall dimensions of the keyboard 10. However, a keyboard structure resulting from such an assumption may cause the operator's fingers when pressing adjacent keys to collide with one another, thus degrading ease in operator's operation of the keys. Such structure also may cause the operator to erroneously press a key different from a key which the operator has attempted to press or to erroneously press a plurality of keys with a single finger. Generally speaking, the horizontal pitch P.sub.2 shown in FIG. 1 between adjacent key tops is preferably more than 15 mm, for example.